Autumn is fast approaching, which means your cosy duvet will be making a triumphant return. While there's nothing like curling up in your bed to fend off the crisp fall nights, it also brings up the age-old question — how often should you change your bed sheets? Well, it turns out there's not a simple answer.

As wellness site Self writes, it all comes down to your sleeping preferences like "how much you move in your sleep to your level of clothing when you hop between the sheets". You also need to consider whether you're sleeping by yourself or sharing the bed with a loved one or pet. There's a lot of gunky stuff and contamination that can accumulate in your sheets over an extended period, including dead skin cells, body oils, drool, and of course, dust mites *shudders*.

If you have acne, it could be something to do with your bed sheets. As dermatologist Whitney Bowe, M.D., told Self, not changing your sheets on the regular "can disrupt your skin's ecosystem", otherwise known as your skin microbiome, due to the number of bacteria making itself at home on your pillowcase. Ew.

So what's the optimum amount of time to go by in terms of washing your sheets? Well, according to experts who provided Self with their knowledge, at least once a week is best. But as microbiologist Michael Schmidt, Ph.D., told the wellness site, "[a] myriad of factors determine if you should wash your sheets more often than once a week based on your lifestyle."

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Of course, there are going to be varying suggestions across the web. Good Housekeeping suggests that washing your sheets can be done "at least once every two weeks", but they also note that if you tend to sweat a lot in bed, "you should increase this to once weekly." This also goes for people who have allergies like hayfever, as pollen can accumulate pretty drastically on your sheets throughout the week. As Self notes, dust mites also factor into this as they "can provoke allergy symptoms like a runny nose, watery eyes, sneezing, and general discomfort that makes it hard to get good rest at night."

In addition to that, Women's Health notes that the American Academy of Dermatology (ADD) "also suggests changing your pillow cases two to three times a week, too".

If you don't have the time — nor the means — to wash your sheets once a week, you can stretch this timeframe out a little longer. As Dr Bowe advised to Self, you should "always wash your face before bed, even if you only applied a moisturiser or sunscreen during the day." A shower before bed is also a good shout, as it can get rid of some of the skin cells that would have flaked off in between your sheets.

The prospect of putting your sheets through the process of washing and drying once a week can seem tedious and off-putting. But once you realise how much gunky stuff comes off your body every night, you may be wanting to dump those sheets in the machine ASAP.